A protocol is presented for a collaborative clinical trail on the relationship between blood glucose and vascular complications of Insulin Dependent Diabetes Mellitus or (IDDM). Phase I represents the collaborative design of Phase II. Phase II is written as a suggested limited feasibility study of establishing two groups of IDDM's. One group would be under intensive care with home blood glucose monitoring and multiple subcutaneous insulin injections or pump insulin delivery while the other group will receive "standard therapy." It is estimated that 80% of the intensive care group will be able to achieve normalization of blood glucose profiles. The degree of control achieved will be documented by hemoglobin A(1)(c) levels, random blood glucose levels in clinic, periodic 24 hour urine glucose excretion, semiquantitative urine testing, and home blood glucose monitored "brackets" in the intensive care group. Outcome criteria in terms of vascular disease will be evaluated by direct measurement of quandriceps capillary basement membrane thickening, pulse volume recordings of the large vessels, urinary protein excretion post exercise, platelet factor 4 and B Thromboglobulin levels as a measure of vascular disease, intensive ophthalmologic examinations, and noninvasive cardiology assessment. Other criteria for risk factors for cardiovascular disease such as blood pressure, lipid profiles, hormonal profiles, and degree of fatness will be measured as well as additional variables of interest to the person with IDDM. In addition to the evaluation of outcome criteria, phase II should provide information regarding the feasibility of establishing near normal blood glucose levels in a group of IDDM so that the feasibility of Phase III - an extended evaluation of the role of blood glucose in vascular disease will be established.